Diabetes is an increasingly prevalent chronic disease whose impact as a public health concern is felt throughout the world. The American Diabetes Association estimates approximately 7% of the United States population suffers from this disease and that 1 out of every 10 dollars spent on healthcare in the U.S. is spent on diabetes and its complications. Type 1 diabetes generally results from the body's failure to produce insulin. Type 2 diabetes is the more prevalent type of diabetes and generally results from insulin resistance combined with a relative insulin deficiency. Additionally, there are millions of Americans who can be said to have prediabetes, that is, higher than normal blood glucose levels but not yet high enough to be diagnosed with Type 2 diabetes.
Type 2 diabetes is characterized by fasting and postprandial hyperglycemia and by relative insulin insufficiency. Hyperglycemia may cause long-term microvascular and macrovascular complications, such as nephropathy, neuropathy, retinopathy, and peripheral vascular disease. In addition, Type 2 diabetes is a comorbid disease that frequently compounds hyperlipidemia, atherosclerosis and hypertension. Hyperlipidemia is a primary risk factor for cardiovascular disease due to atherosclerosis. Obesity is a well known common risk factor for the development of atherosclerosis, stroke, hypertension and Type 2 diabetes. Type 2 diabetes causes significant morbidity and mortality at considerable expense to patients, their families and society. Furthermore, the incidence of Type 2 diabetes worldwide is increasing such that Type 2 diabetes is now considered to be a worldwide epidemic.
A number of therapies for the treatment of Type II diabetes are in use. A change in diet along with an increase in exercise and weight loss is considered a first line of treatment. However, this may not result in sufficient control of blood glucose levels resulting in the use of medications to help control glucose levels. These medications include insulin, sulfonylureas, meglitinides, biguanides, thiazolidinediones, DPP-4 inhibitors, alpha-glucosidase inhibitors, amylin analogs and incretin mimetics. These medications may be used singly or in combination and may result in reduced glucose levels. However, these medications still may not cause a drop in glucose levels to what would be considered normal or the effect may wear off over time. Some medications may lower glucose levels too much, resulting in a dangerous hypoglycemic episode. Insulin, amylin and incretin mimetics need to be injected, often numerous times a day. Other side effects include weight gain, nausea, and diarrhea.
GPR119 is a class 1 G-protein-coupled receptor which has received attention due to evidence that modulation of the GRP119 receptor may produce favorable effects on glucose homeostasis, food intake, body weight gain and β-cell preservation, any or all of which effects may be useful in the treatment of both diabetes and obesity (Br. J. Pharm. 2007 1-6).
The GPR119 receptor and isoforms have been identified in mammalian species including human, rat, mouse, hamster, chimpanzee, rhesus monkey, cattle and dog. The pancreas has been identified as the major site of mRNA expression in the human, with some expression also seen in the gastrointestinal tract. The expression of GPR119 in the pancreas and particularly in the pancreatic β-cells led to the hypothesis that the GPR119 receptor could have effects upon insulin secretion.
The discovery of two endogenous ligands, lysophosphatidylcholine (LPC) and oleoylethanolamide (OEA) as well as more potent GPR119 agonists have led to the characterization of GPR119 as both an insulin and incretin (GLP-1 and GIP) secretagogue receptor capable of lowering plasma glucose and thereby facilitating glycemic control without the risk of hypoglycemia (Biochem. Biophys. Res. Comm 2005 744-751, Cell Metabolism 2006 167-175, Endocrinolgy 2007, 2601-9, Endocrinology, 2008, Epub ahead of print). GPR119 knockout animals have shown that both insulin and incretin secretion induced by GPR119 agonists are dependent upon GPR119 receptor. In addition, it has been shown that GPR119 agonists decrease food intake resulting in weight loss in Sprague Dawley rats. Taken together, GPR119 is a novel mechanism by which glycemic control may be facilitated with the added benefit of weight loss.